WASTEWATERBy Rick LallishWhat is the most common type of lagoon in use to treat municipal wastewater?A. Anaerobic lagoonB. Aerated lagoonC. Polishing lagoonD. Facultative lagoonAnswer: D. The most common lagoon treatment system is the facultative lagoon. These lagoons are typically 3 to 8 feet deep. They have dual layers: an upper aerobic layer and bottom anaerobic layer. The algae in the aerobic layer supply dissolved oxygen. Light penetration determines the aerobic layer’s depth. The waste byproducts from the aerobic layer trickle down to the anaerobic layer, where digestion takes place. The layers supplement each other. Controlled discharges from these lagoons may provide detention times of
